This invention relates to an apparatus for preventing lubricating oil for a Stirling engine from rising along the cylinder of the engine and reaching the working spaces thereof. More particularly but not exclusively, it relates to an apparatus for preventing the rise of oil in a displacer-type Stirling engine having a piston and a displacer coaxially disposed within the same cylinder.
In a Stirling engine, a portion of the lubricating oil for the crankshaft and the piston is formed into a fine mist by the reciprocating motion of the crosshead, piston rod, piston, displacer rod, and other moving parts of the engine. Despite the provision of seal rings on the piston and various seal devices between the piston and the displacer, the mist of lubricating oil is able to penetrate the working spaces of the engine, from where it enters the heat exchanger. As the presence of oil in the heat exchanger greatly reduces the efficiency of the engine, there is a need for an apparatus which can effectively prevent oil from rising to the working spaces of a Stirling engine.